Northwest Territories Geological Survey

The Government of the Northwest Territories (GNWT) wants to expand the Taltson hydroelectric system in the territory’s South Slave Region, and connect it to the North Slave Region’s hydroelectric system. Connecting the two hydro systems would create a secure, reliable, green power grid that could supply almost 75% of the NWT’s community power demands.

This expanded and connected grid could also supply territorial resource development projects with clean energy. Despite a lack of roads, electrical transmission lines and communication corridors to support it, the mining sector is the backbone of the NWT economy. Accessible hydroelectricity would dramatically reduce the mining industry’s carbon emissions as well as their operational costs.

The Taltson River system has the potential to support 200 Megawatts (MW) of electricity generation capacity. The existing 18 MW hydro plant on the Taltson River could be accompanied by a new 60 MW plant utilizing existing water storage with no new flooding, and could deliver green energy to market within five to ten years.

The GNWT is currently undertaking a study to examine using High Voltage Direct Current (HVDC) and submarine cables to link the South Slave Region—which is rich in hydro resources—to the mineral-rich and high-load North Slave Region, where there is heavy resource development. The idea of connecting these two areas is not new. A Western Great Slave Lake Transmission Line and various AC submarine and overhead cabling routes were studied in the past, but today, using HVDC could provide superior performance and lower costs.

Most transmission lines are High Voltage Alternating Current (AC), which is generally the lowest cost option. Although HVDC transmission has superior technical properties, it can be more expensive. To interface with the AC grid, expensive converter stations are needed to convert electricity from AC to Direct Current (DC) and back again. Historically, HVDC was only economic for large power transfers over a long distance, or used where a long underwater cable was required. However, technological advances in recent years have created new HVDC solutions targeting smaller installations, although many of these installations are still in the hundreds-of-megawatts range.

For this project, an HVDC connection would reduce the overall cable size and the number of submarine cables needed (two vs. three). Lighter cables, with a greater length per cable reel means fewer cable joints. Cable joints are a potential point of failure in submarine cables, and represent a significant cost in labour and materials. Other challenges this study will examine include how to get cable-laying equipment to the location (traditional cable-laying vessels are not able to travel down the Mackenzie River), and the limited installation period due to the annual ice-up on Great Slave Lake.

Future work will include community engagement, environmental assessment, commercial prospects, and technical elements such as bathymetric studies. If feasible, an HVDC submarine cable route could enable connection to remote mine sites that are dependent on diesel fuel for electrical generation, resulting in significant economic and greenhouse gas reduction benefits.